Two-cycle engine



,April 18, 1939.4 L DUFQUR 2,154,975

TWO- C YCLE ENGINE Filed Feb. 18, 1957 111111111 '11114 rlllllllrllzl Patented API'- 18, 1939 l t UNITEDl s'rA'riisl PATENT OFFICE TWO-CYCLE ENGINE Lon Dufour, Versoix, Switzerland Application February 18, 1937, Serial No. 126,460 In Germany December 29, 1936 s claims. (ci. 12a-e5) This invention relates to two-cycle engines of Figures 3 and 4 are twoanalogous views illusthat type in which the cylinder head forms a. trating a modified form of the invention. chamber in the shape of an open spiral which 'Ihe engine according to Figs. 1 and2 comprises ends approximately into a fragment of a cylina crank shaft having its axis at I, a flywheel 2 der. The purpose of the provision of such a carried by the crank shaft, a crank 3 connected 5- chamber is to make use of the high velocity of by means of the connecting rod 4 to the piston the fresh charge entering into the cylinder to 5, A closed crank case AI3 forms together With create in the approximately cylindrical portion the internal surface of the piston 5 the suction, of the head a whirl which retains the fresh gascharging and scavenging pump. The engine cylm ecus charge in the cylinder head and in the upinder 1 Carries a cylinder head 8 in which is 1o per portion of the cylinder and prevents escape formed a Chamber 9 having the Shape 0f an Open of the fresh charge together with the burnt gases Spiral the innelmOSt DOitiOn 9 of which forms through the exhaust ports. approximately a fragment of a cylinder. The The object of the invention is the provision fresh gaseous charge arrives through a pipe I0 of means for maintaining the whirling motion and a port II into the crank case when this POIt 15 of the fresh charge at high velocity until and iniS uncovered by the piStOil arriving at the top end cluding the ignition period whereby ignition of of its stroke. .A transfer passage l2 delivers the the charge is facilitate@ i compressed charge into the cylinder. The ex- The invention consists in the provision of a haust port I3 and inlet port l2 are successively two-cycle engine of the above mentioned type uncovered by the piston when it arrives at the 20 in which the diameter 0f the approximately cylower end of its stroke and are covered again lindr-ical portion of the spiral-shaped chamber when the piston rises. A spark plug will be inhas a length equal to one half tov one quarter serted in the hole I4 in the cylinder head.

of the diameter of the engine cylinder, While the It will be seen that the diameter d of the cypiston head and that surface of the cylinder lindrical portion 9' 0f the Chamber 9 is approxi- 25 head connecting 4the .final point of the spiralmately equal t0 One quarter 0f the diameter D shaped surface of the head with the exhaust side of the cylinder Thc spiral-shaped surface of of the cylinder wall are so arranged that when the chamber 9 ends irltO a nOSe 2| which is conthe piston has arrived at the end of its compres- IleCted by means 0f a Slightly Curved Surface I5 sion stroke', a channel is formed between the pis- With that side of the cylinder Wall on which is 30 ton and said surface portion of the head, which provided the exhaust port I3. The piston head channel opens in a direction which is substanis provided with-a projection formed on one side tially tangential to the spiral into said spiralby a surface I6 showing the same curvature as shaped chamber, so that the stream of the fresh the surface I5 on the cylinder head, and 0n the charge directed into the cylinder head by said -Other side by a vertical surface I1. The cham- 35 channel causes the whirl to continue its moveber 9 iS Provided With aASllIfaCe i3 approaching ment of gyration at high -velocity during the iga Plane, that iS t0 Say ShOWiIlg a Slight Curvanitionv period. I have effected numerous tests ture 0h13?, this Surface i8 COIlIleCtiIlg the cham- Which prove that the chamber in the Cylinder ber with that side of the cylinder wall which is head must'have the above mentioned dimensions Situated Opposite the exhaust Port- 40 in order to obtain the desired resu1t,whi1e at the In the' moment When the fesh engere@ is de' same time care must be taken that the fresh hved mto the cylinder the piston 1s m lts lower l charge directed into the cylinder head during the postumi) as Shown, m mg' 1 That gaseous laiyer compression stroke of the piston does not coun- Whlch 1S nem. the penphery of the cyhnder rises teract the Whirl in the chamber but in the com along the cylinder Wall and flows then along the f I to the ch mber trary, contributes to maintain the whirling mongg a gvlung motio'l meglagfsrflaggnus tion.

char e risin in the interior of th c ln Reference is had to the accompanying drawg g e y 1 der nearer to its axis, impinge against the surface I8, lng whichA illustrates two forms of the invention. and owing to the slight curvature of this surface, 5o

Figure 1 is a Vertical medial Section through these layers are not projected backwards into a Single Cylinder engine embOdYirlg the inventionthe cylinder, but also towards the chamber 9, Figure 2 is a cross Section through the cylinsubstantially according to the 1ine a-b-c, and der 'at the height of the transfer and exhaust are also caused to follow the whirling motion in ports. the chamber 9'. This motion maintains during 55 the charging period the fresh charge in the cylinder head and in the upper part of the cylinder and prevents the escape of fresh gases through the exhaust port together with the burnt gases. It is however also important that the whirl continues its movement of gyration at high velocity until and including the ignition period, in order that those portions of the charge situated near the spark plug in the moment of sparking and which are immediately ignited, are thrown at a high velocity into the interior of the mass of Whirling gases. In this manner ignition is communicated much more rapidly to the entire charge than it would be owing to the-speed o f propagation only of the flame in lthe charge, and no knocking noise occurs during the ignition period, even if much higher compression ratios are used than it was customary heretofore. Experience has shown that the 'high velocity of the whirling motion can best be maintained during ignition when the cylindrical portion 9' of the chamber 9 has such dimensions that its diameter d is comprised between one half and one quarter of the diameter D of the cylinder. This cylindrical portion must be relatively small in order that the speed of the movement of gyration of the charge is high, but if the diameter d would be too smalL a portion of the fresh charge would not enter into this cylindrical chamber and would accordingly not participate at the whirling motion. Also the whirl must not be disturbed by the fresh gases which are forced into the chamber 9 by the piston during its compression stroke. For this purpose the surfaces I5 and I6 are so shaped that they form a channel when the piston arrives at the end of the compression stroke, which channel opens into the chamber 9 in substantially tangential direction to the cylindrical portion 9 of this chamber. The gases flow in the direction of the arrow f1 into the chamber and contribute to maintain or even accelerate the movement of gyration of the gases in the cylindrical portion of the chamber.

In the example according to Figs. 2 and 3 the cylinder head 8 is similar to that described with reference to Fig, 1. The cylinder 'I is provided with two transfer passages 20 and 20' disposed on either side of the exhaust port I3, so that two streams of fresh gases enter the cylinder and rise in inclined direction to meet in the upper portion of the cylinder opposite the exhaust port. The

head of the piston is provided with a projection 22 limited on the right hand side by a surface I6 which is curved to be parallel with the surface I5 of the cylinder head, and on the left hand side by a surface I9 which is parallel with the surface I8 of the cylinder head. When the piston arrives at the end of the compression stroke, not only the faces I5 and I6 form a channel as in Fig. 1, but also the faces I8 and I9 form a channel which urges the fresh gases in tangential direction into the chamber 9'. In this manner the fresh charge compressed by the piston flows towards the chamber 9' according to the arrow f1 on the right side and according to the arrow f2' on the left side of the piston and contributes to maintain and possibly to accelerate the whirling motion in the chamber.

In order to simplify the drawing, an elementary two-cycle engine with one cylinder and with crank case suction and compression of the charge has been shown. It is well known that this type of engine has the disadvantage that the charge dra'wn fromv the carburetor and pumped into the cylinder produces only an incomplete cylinder filling, and that difliculties of lubrication are experienced. The invention can however be applied as well to engines in which the piston controls the inlet and exhaust ports, but in which an independent pump for charging the cylinders is used. For this purpose a single acting or double acting piston pump could be used, or a rotary or .let and exhaust ports in the cylinder, a cylinder head forming an explosion chamber, the wall of said chamber being constructed as a spiral beginning at the side of the cylinder opposite the exhaust port, the inner end of said chamber forming a substantially cylindrical pocket, saidV pocket being offset relative to the axis of the cylinder and being terminated by a nose extending above the internal Apart of the cylinder, the cylinder head having a .downwardly extending, curved surface connecting said nose of the cylindrical pocket to the exhaust port side of the cylinder wall, a deflector on the top of the piston for directing the stream of fresh gases towards the spiral wall of the explosion chamber and into said cylindrical pocket to form therein a whirling movement, said deilector being arranged to arrive laterally of the cylindrical pocket when the piston isl at the end of the compression stroke and to substantially confine the compressed charge in said pocket without penetrating into the cylindrical area of the pocket and disturbing the whirling movement of the compressed charge.

2. A two-cycle internal combustion engine of the spark ignition type, comprising a cylinder, a piston operable therein, piston controlled inlet and exhaust ports in the cylinder, a cylinder head forming an explosion chamber, the wall of said chamber beginning at that side of the cylinder along which the charge of fresh gases rises into the explosion chamber being constructed as a spiral, the cylinder head having a downwardly extending curved surface connecting the nose of said spiral-shaped surface to the exhaust port side of the cylinder wall, the'inner end of said explosion chamber forming a substantially cylindrical pocket having a diameter of substantially one half to one quarter of the diameter of the cylinder, the top of the piston being provided with a deflector for directing the charge of fresh gases towards the explosion chamber, the cylindrical pocket of the chamber being sufficiently offset relative to the axis of the cylinder towards the side opposite the .arrival of the fresh charge, whereby said deflectorre'mains laterally ofthe cylindrical pocket of the explosion chamber when the piston is at the end of its compression tion to the whirling movement of the fresh charge in this chamber.

3. A two-cycle internal combustion engine of thespark ignition type, comprising a cylinder, a piston operable therein, piston controlled inlet and exhaust ports in the cylinder, a cylinder head forming an explosion chamber, the wall of said chamber beginning at that side of the cylinder along which the charge of fresh gases rises into the explosion chamber being constructed as a spiral, the cylinder head having a downwardly extending curved surface connecting the nose of said spiral-shaped surface to the exhaust port side of the cylinder wall, the inner end of said explosion chamber forming a substantially cylindrical pocket having a diameter of substantially "one half to one quarter of the diameter of the cylinder, the top of the piston being provided with a deilector for directing the charge of fresh gases towards the explosion chamber, the cylindrical pocket of the chamber being slightly offset relative to the axis of the cylinder towards the side opposite the arrival of the fresh charge, but not extending beyond the circumference of the cylinder. whereby said deflector remains laterally of the cylindrical pocket of the explomon chamber when the piston is at the end of its compression stroke, the deflector having a curved surface extending substantially parallel to said curved surface of the cylinder head between the nose of the spiral-shaped surface and the cylinder wall, said two surfaces cooperating with each other at the end of the compression stroke of the piston to form a channel beginning at the exhaust port side of the cylinder and opening into the explosion chamber in substantially tangential direction to the whirling movement of the fresh charge in this chamber.

tending substantially parallel to that portion of 3 the spiral-shaped wall of the explosion chamber situated adjacent to the side of the cylinder along e which the charge of fresh gases rises into the chamber, and cooperating with said spiralshaped wall portion at the end of the compression stroke of the piston to form a second 'channel beginning at the side of the cylinder opposite the exhaust port and opening into the explosion chamber in substantially tangential direction to the whirling movement of the charge in this chamber.

5. A two-cycle internal combustion engine comprising a cylinder, a piston operable therein, inlet and exhaust ports in the wall of the cylinder and adapted to be intermittently covered and uncovered by the piston at the lower end of its stroke, an inlet port being provided on either side of the exhaust port, av cylinder head forming a chamber in the shape of an open spiral, the inner end of said spiral-shaped chamber forming approximately a fragment of a cylinder, a gaseous charge being directed from said inlet ports upwardly into the cylinder head and caused to form a whirl in said approximately cylindrical portion of the spiral-shaped chamber, the diameter of said approximately cylindrical portion being comprised between one half and one quarter of the diameter of the cylinder, the cylinder head having a surface connecting the inner end of the spiral-shaped surface to the exhaust port side of the cylinder wall and a surface connecting the spiral-shaped chamber to the wall portion of the cylinder situated opposite the exhaust port, said second surface presenting a slight curvature only whereby the upwardly movingilowofgaseischargeimpinsinsonsaid surface is directed towards the spiral-shaped chamber, the top of the piston being provided with two surfaces coacting one with said first mentioned surface of the cylinder head and the other with said second mentioned surface of the cylinder head to form two channels when the piston is at the end of its compresion stroke, each channel opening into said spiral-shaped chamber in substantially tangential direction to thespelrailymovingfiowofthcgasecuscharge.A

Laon Dumon. 

